Information for small house enthusiasts.

Basic Electrical How To

25 Nov, 2011

In this article we’re going to cover some electrical ‘how to’ pointers so that your wiring is easier to install and to ensure that it meets electrical codes.

Running electrical wires is easiest in new construction before the drywall is installed. Drill holes in the center of each stud to run wires horizontally between boxes. If you can’t run the wire through studs near the center of the stud, you can cut notices in the surface of the stud deep enough to receive the wire. Protect the wire from possible damage from screws or nails by fastening a nailing plate over the wire, as required by code. When running wire vertically along a stud, building codes require that you fasten it to the center of the stud with wire fasteners every four feet and within 12” of an electrical box.

Common Old-Work Boxes

This is a single gang (only allows one outlet or switch installed in it) old-work box, also known as a remodel box because it’s often used when a new outlet or switch is needed in an existing wall. Notice the tab at the top right corner of the box. It has a corresponding tab on the bottom edge also. This is what holds it to the drywall from the inside.

This is a 2-gang old-work box.

This is a round old-work box. It’s used in ceilings where a fixture is needed. The downside of using this box is that it can only hold up to about 15 pounds, so no ceiling fans here!

When you want to add an electrical outlet to an existing room, but you don’t want to damage your walls to do so, you need a few tricks up your sleeve. The difficult part of running any wire behind an existing wall is threading the new wire through the electrical box, so some patience and skill is required to fish through to the openings in the electrical box. Sometimes it is easier to remove the existing box and replace it with an ‘old work’ box as you complete the project.

You need to use an ‘old work’ box in which to run your wire and receptacle. An old work box has flanges on the top and bottom of the box that hold the box against the outside of the wall while two tabs are tightened by screws to hold it in place. The hole for the box has to be cut precisely to accommodate these flanges. If it is cut too big, the flanges will not catch the wall and your electrical box will not be securely fastened — a code violation.

Once you have cut the hole for the electrical box, you then need to feed the wire to the hole in the wall, don’t set the box into the hole until you have run the wire. The easiest way to run new wire behind an existing wall is to use a crawl space below or attic space above the wall. Drill holes about 1” in diameter through the floor or ceiling plate in the same wall stud cavity as the new box and the existing box from which you are running the wire. Push your fish tape behind the wall from the hole in the plate to the hole for the electrical box that you are adding. Work from the smaller hole to the bigger hole and from top to bottom if possible, to make the job easier.

Having an assistant is usually necessary for this part of the job. Attach the new wire that you are running to the fish tape with electrical tape and thread the wire through both holes, but don’t cut it yet. Thread the fish tape through the other wall cavity to the existing electrical box using the same procedure as before, and you will have successfully run an electrical wire behind an existing wall without damage. Now pull the wire through the new ‘old work’ box and tighten the box into position. Code does not require that wire run behind an existing wall be fastened, because the ‘old work’ box has a one way wire fastening device. Use fire block caulk to seal any penetration between floors as required by code, for safety.

When you want to run a new wire horizontally behind an existing wall, you can buy a drill bit with a flexible 4 feet long shaft that can be bent with a special tool (provided with the bit) to drill through the studs behind drywall. You can add extensions to the drill bit to drill extended holes. Once you have reached the stud cavity from which your wire is run, just attach the new wire to the drill bit and pull the wire through as you withdraw the drill bit.

Electrical wiring is one of the essentials of ‘electrical how to’. Making sure that your wiring is up to code is essential, too.

editor’s note: Please double check electrical work against the National Electric Code for safety.